why i HATE shared NEUTRALS!!

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I didn?t see anything in either site that stated any danger in a MWBC. Did anyone find something that I might have overlooked? :?

Personally I think that the MWBC is the only way to fly and have never before this thread heard of a problem except to the untrained.
:)
 
iwire said:
Copper org would get behind that change. :p
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Yea, what with all the plumbing business going to PEX tubing, they're looking for new customers for big, fat pieces of copper. :)
 
Mike, I didn't see anything "against" MWBC'S either. Brother, I think you need to read your links again.

Ninety five percent of the conduits leaving the panels in the pictures below have 4 wire MWBC's in them and this is just one electrical closet of hundreds (yes really hundreds) in a hospital we work at. I can and will swear under oath that we have never had a call back due to an open neutral of a MWBC in the 11 years I have been doing projects in this facility, and we are literaly talking thousands of circuits

CR-EQsystems.JPG


NORMsystems.JPG


The bottom line is they are safe, conservation friendly, practical, saves money for the party paying the electric bill, etc...

The reality is, problems occur when the wrong people are doing the work, or are not being supervised, this could also be the case of a Mechanic that doesn't know what he/she is doing, they can get you out the door, but their fix will break not to far down the road.


Roger
 
I understand that proposals for the 2008 code that will require handle ties on all MWBCs and also require group identification of the hots and grounded conductors at the panels have been approved.
Don
 
Don, I have a feeling that it will not stand, there are to many instances, (such as in a hospital) where circuits can not or would not be practicle to be turned off or opened at the same time.

I do think it would stand a chance for dwellings though.

Roger
 
roger said:
Don, I have a feeling that it will not stand, there are to many instances, (such as in a hospital) where circuits can not or would not be practicle to be turned off or opened at the same time.

I do think it would stand a chance for dwellings though.

Roger
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Would not fly in factories either.While neutrals could be dedicated in a home it is almost imposable in commercial.They cause no problems till they go bad and i have seen some fail.
 
Thank you Michael, it was a very good crew that put this job in.

I do need to make a correction to my post though, after counting the closets in my mind per floor and campus I probably should have said over a hundred electrical closets, hundreds may be stretching it although two hundred is very probable, just wanted to clarify that. :wink:

Roger
 
Don,
I too can imagine several instances where something as simple as a handle tie would cause (in my opinion) an unnecessary burden. Thank you for enlightening us. Question, is there a 'public feedback' mechanism of some type, where we could raise questions about this proposal.
 
roger said:
Thank you Michael, it was a very good crew that put this job in.

I do need to make a correction to my post though, after counting the closets in my mind per floor and campus I probably should have said over a hundred electrical closets, hundreds may be stretching it although two hundred is very probable, just wanted to clarify that. :wink:

Roger
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I agree the pipe work looks great,but buy a label machine.Blue painters tape is kinda cheap
 
Jim, I guess this is just a little over your head. If it isn't apparent to you in the pictures, let me explain, this was an ongoing project and upon completion there are color coded Phenolic Labels made for each panel and system identifying the voltage and where they are fed from, IE Critical Branch, Life Safety Branch, Equipment Branch, Normal Branch etc... these colors are painted on the conduits leaving the panels (as you can see) and through out the ceilings as well as the junction boxes. This project had over a thousand dollars in labels alone.

Label machines look kind of cheap in reality, but if they make you happy all I can say is, good for you. :roll: :roll: :roll: I guess in your area (FL) label machines are state of the art. :lol:

Roger
 
don_resqcapt19 said:
I understand that proposals for the 2008 code that will require handle ties on all MWBCs and also require group identification of the hots and grounded conductors at the panels have been approved.
Don
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That would just plain suck. How on earth would I then be able to run ckts. 1, 4 and 42 with a single neutral if they did something crazy like require tiebars on the breakers? Some people just don't think before they throw out these dumb proposals. :roll:
 
dnem said:
So for you guys doing multis on minis. Don't let yourself go thru the motions on autopilot while you're landing the panel. I've found even good electricians that have made that mistake.
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I've seen it too. Once I witnessed the panel being trimmed out, and that guy has more experience than I do, and he goofed. At a different location I saw it where I didn't know who originally trimmed out the panel.

I'm pretty sure in the second panel the 42-handle rule had flown out the window, as well. :shock: :(

There were cubicle units originally breakered all on one phase - one phase wasn't even accidentally right. :(

That said, the method is sound. It's just when people zone out, or are just plain uneducated, that's when we start running into problems. :?
 
So...you are correct in stating that two 120 volt circuits can share the same neutral...as long as they are on different busses...but there is no defined requirement that the handles be tied or locked together (often the 2 different breakers are in different parts of the panel and can not be tied together)....but it must be clearly indicated that each circuit shares a neutral with the other at the panel and all boxes and junction boxes downstream. Anytime you are working on one circuit...it's shared neutral counterpart circuit must also be off....or shock potential exists.
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210.7(C)


http://www.mikeholt.com/PopGraphic.php?id=1252

Read this on the site that was posted .

We share neutrals all the time. I know of 2 incidents for our company that people have been shocked severely and both cases had to do with not shutting the power off to begin with.

BTW I love this site so much cause everyone quotes code. I have learned a great deal from it.
 
Ok, im bringin it on. LOL :D

I know i wont change minds but this is something i just wanted to print it. Something to argue, oops i mean think about. :wink:


On May 12, 2005, at the Hanford Plutonium Finish Plant an electrician received an electric shock :shock: from the neutral wire while terminating the wire on a relocated electrical panel. Voltage did not show during the zero-energy check because the neutral wire created a complete circuit through the neutral bus. The voltage potential to ground was identified only after the neutral wire was de-terminated. Investigators determined that the neutral belonged to a security circuit in a different panel. In the early 1990's an electrician had relocated a 120v securtiy camer circuit but did not wire it according to plan
 
roger said:
Jim, I guess this is just a little over your head. If it isn't apparent to you in the pictures, let me explain, this was an ongoing project and upon completion there are color coded Phenolic Labels made for each panel and system identifying the voltage and where they are fed from, IE Critical Branch, Life Safety Branch, Equipment Branch, Normal Branch etc... these colors are painted on the conduits leaving the panels (as you can see) and through out the ceilings as well as the junction boxes. This project had over a thousand dollars in labels alone.

Label machines look kind of cheap in reality, but if they make you happy all I can say is, good for you. :roll: :roll: :roll: I guess in your area (FL) label machines are state of the art. :lol:

Roger
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Nice job Roger. We do the same thing. We usually install all the phenolic labels near the end of the project. This could be months after the panel trims get installed. We always use blue painters tape for temporary labeling. It usually peels right off which makes it rather simple to install the permanent labels. I have seen guys use permanent markers to write on the panel trims as temporary labels. It stinks for the guy who has to come by with a bucket of GOJO and some rags to rub the marker off.
 
brother said:
Ok, im bringin it on. LOL :D

Investigators determined that the neutral belonged to a security circuit in a different panel. In the early 1990's an electrician had relocated a 120v securtiy camer circuit but did not wire it according to plan
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I'm not an expert, but I don't think that this example fits. I mean, yes, technically it is a MWBC. But come on - it's from two different panels!!! (Kinda hard to have handle ties for those circuits!)

I believe that a horror story could be found that would shed bad light on almost anything that we do.
 
I agree with Minuteman. It makes a strong case for retooling some safety procedures, but doesn't spell death for the MWBC in my book.

There are so many different ways to get shocked this way, I'd say the most effective weapon against it is preparedness, rather than banning MWBC's starting today. Who would expect a neutral snagged from a different panel? That's a violation of code anyway: 300.3(B). :)
 
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